In-vitro antibacterial activity of L-105, a new cephalosporin

L-105 (sodium(-)-(6R, 7R)-7-[(Z)-2-(2-amino-4-thiazolyl)-2-methoxyimino- acetamido]-3-[1,2,3-thiadiazol-5-yl)thiomethyl]-8-oxo-5-thia-1-aza bicyclo [4.2.0]oct-2-ene-2-carboxylate) is a new semisynthetic cephalosporin derivative. The in-vitro antibacterial activity of L-105 against clinical isolates of 18 bacterial species was compared with those of cefmenoxime, cefoperazone and cefazolin. Its spectrum against Gram-negative bacteria was similar to that of cefmenoxime. Moreover, against Gram-positive bacteria, including Staphylococcus aureus, coagulase negative staphylococci, Streptococcus faecalis, Str. pneumoniae and Str. pyogenes, L-105 was more potent than cefmenoxime and cefoperazone. Against Gram-positive bacteria, including Staph. aureus which is comparatively resistant to most third-generation cephalosporins, it was nearly equal in potency to cefazolin. L-105 was stable to various penicillinases and cephalosporinases. However, this compound was slightly hydrolyzed by oxyiminocephalosporinases, i.e., the enzymes produced by Pseudomonas cepacia and Ps. maltophilia.